New species evolve whenever a lineage splits off into several branches and so a common metaphor for evolution has been to describe evolution as a 'tree of life', where every branch constitutes a species.

But since about 99.999% of all species that have ever existed are already extinct, and we have never even known about them, the tree is more like a bush with things constantly growing and falling off. Last year, a consortium of some hundred researchers reported that the relationship between all major bird clades had been mapped out by analyzing the complete genome of around 50 bird species. This included the exact order in which the various lineages had diverged.

Both donors and recipients want more information about each others' health before participating in transplant surgeries, according to a study which challenges current practices and policies on information disclosure for prospective living kidney donors and their intended recipients..

For students, the start of the school year means new classes, new friends, homework and sports. It also brings the threat of head lice. The itch-inducing pests lead to missed school days and frustrated parents, who could have even more reason to be wary of the bug this year. Scientists report that lice populations in at least 25 states have developed resistance to over-the-counter treatments still widely recommended by doctors and schools.

The researchers are presenting their work today at the 250th National Meeting&Exposition of the American Chemical Society (ACS), the world's largest scientific society. The meeting features more than 9,000 presentations on a wide range of science topics and is being held here through Thursday.

A team of researchers has discovered a Jupiter-like planet within a young system that could provide a new understanding of how planets formed around our sun.

The new planet, called 51 Eridani b, is the first exoplanet discovered by the Gemini Planet Imager (GPI), a new instrument operated by an international collaboration headed by Bruce Macintosh, a professor of physics in the Kavli Institute at Stanford University. It is a million times fainter than its star and shows the strongest methane signature ever detected on an alien planet, which should yield additional clues as to how the planet formed.

Dosing obese teens with vitamin D shows no benefits for their heart health or diabetes risk, and could have the unintended consequences of increasing cholesterol and fat-storing triglycerides. These are the latest findings in a series of Mayo Clinic studies in childhood obesity.

Seema Kumar, M.D., a pediatric endocrinologist in the Mayo Clinic Children's Center, has been studying the effects of vitamin D supplementation in children for 10 years, through four clinical trials and six published studies. To date, Dr. Kumar's team has found limited benefit from vitamin D supplements in adolescents. The latest study, Effect of Vitamin D3 Treatment on Endothelial Function in Obese Adolescents, appears online in Pediatric Obesity.

Sepsis kills more Americans every year than AIDS, breast cancer and prostate cancer combined but it gets far less attention. Unlike those other diseases, hours can make the difference between life and death in sepsis.